SQL & PL/SQL

We use a query like this on Oracle 11.2g (in a PL/SQL stored procedure):

WITH x AS ( SELECT /*+materialize*/ FK1ID, FK2Id, FK3Id  FROM SOME_VIEW  WHERE some_ID = p_some_parameter) -- an IN parameter of the stored procedure
  SELECT  foo, bar, baz FROM t1, t2, ...
  WHERE exists (
    select 1 from  x where 
        x.FK1ID= 42
      or
        x.FK1ID = 34 and
        x.FK2ID = t2.xyz)
    AND some other conditions

This is much faster (50 times) than without the +materialize hint or if we put that (sub)query in line.

But apparently it causes extra I/O (writing the subquery result to temporary table and reading it back).

Is that true? If yes, what else to use instead then?

Regards,
David

PS: The subquery would have 10-20 rows, while the main query would return tens of thousands of rows in our test case.